/*
** $Id: lcorolib.c,v 1.10.1.1 2017/04/19 17:20:42 roberto Exp $
** Coroutine Library
** See Copyright Notice in lua.h
*/

#define lcorolib_c
#define LUA_LIB

#include "lprefix.h"

#include <stdlib.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"

static lua_State* getco(lua_State* L)
{
    lua_State* co = lua_tothread(L, 1);
    luaL_argcheck(L, co, 1, "thread expected");
    return co;
}

static int auxresume(lua_State* L, lua_State* co, int narg)
{
    int status;
    if (!lua_checkstack(co, narg))
    {
        lua_pushliteral(L, "too many arguments to resume");
        return -1; /* error flag */
    }
    if (lua_status(co) == LUA_OK && lua_gettop(co) == 0)
    {
        lua_pushliteral(L, "cannot resume dead coroutine");
        return -1; /* error flag */
    }
    lua_xmove(L, co, narg);
    status = lua_resume(co, L, narg);
    if (status == LUA_OK || status == LUA_YIELD)
    {
        int nres = lua_gettop(co);
        if (!lua_checkstack(L, nres + 1))
        {
            lua_pop(co, nres); /* remove results anyway */
            lua_pushliteral(L, "too many results to resume");
            return -1; /* error flag */
        }
        lua_xmove(co, L, nres); /* move yielded values */
        return nres;
    }
    else
    {
        lua_xmove(co, L, 1); /* move error message */
        return -1;           /* error flag */
    }
}

static int luaB_coresume(lua_State* L)
{
    lua_State* co = getco(L);
    int r;
    r = auxresume(L, co, lua_gettop(L) - 1);
    if (r < 0)
    {
        lua_pushboolean(L, 0);
        lua_insert(L, -2);
        return 2; /* return false + error message */
    }
    else
    {
        lua_pushboolean(L, 1);
        lua_insert(L, -(r + 1));
        return r + 1; /* return true + 'resume' returns */
    }
}

static int luaB_auxwrap(lua_State* L)
{
    lua_State* co = lua_tothread(L, lua_upvalueindex(1));
    int r = auxresume(L, co, lua_gettop(L));
    if (r < 0)
    {
        if (lua_type(L, -1) == LUA_TSTRING)
        {                     /* error object is a string? */
            luaL_where(L, 1); /* add extra info */
            lua_insert(L, -2);
            lua_concat(L, 2);
        }
        return lua_error(L); /* propagate error */
    }
    return r;
}

static int luaB_cocreate(lua_State* L)
{
    lua_State* NL;
    luaL_checktype(L, 1, LUA_TFUNCTION);
    NL = lua_newthread(L);
    lua_pushvalue(L, 1); /* move function to top */
    lua_xmove(L, NL, 1); /* move function from L to NL */
    return 1;
}

static int luaB_cowrap(lua_State* L)
{
    luaB_cocreate(L);
    lua_pushcclosure(L, luaB_auxwrap, 1);
    return 1;
}

static int luaB_yield(lua_State* L) { return lua_yield(L, lua_gettop(L)); }

static int luaB_costatus(lua_State* L)
{
    lua_State* co = getco(L);
    if (L == co)
        lua_pushliteral(L, "running");
    else
    {
        switch (lua_status(co))
        {
        case LUA_YIELD:
            lua_pushliteral(L, "suspended");
            break;
        case LUA_OK:
        {
            lua_Debug ar;
            if (lua_getstack(co, 0, &ar) > 0) /* does it have frames? */
                lua_pushliteral(L, "normal"); /* it is running */
            else if (lua_gettop(co) == 0)
                lua_pushliteral(L, "dead");
            else
                lua_pushliteral(L, "suspended"); /* initial state */
            break;
        }
        default: /* some error occurred */
            lua_pushliteral(L, "dead");
            break;
        }
    }
    return 1;
}

static int luaB_yieldable(lua_State* L)
{
    lua_pushboolean(L, lua_isyieldable(L));
    return 1;
}

static int luaB_corunning(lua_State* L)
{
    int ismain = lua_pushthread(L);
    lua_pushboolean(L, ismain);
    return 2;
}

static const luaL_Reg co_funcs[] = {{"create", luaB_cocreate},
                                    {"resume", luaB_coresume},
                                    {"running", luaB_corunning},
                                    {"status", luaB_costatus},
                                    {"wrap", luaB_cowrap},
                                    {"yield", luaB_yield},
                                    {"isyieldable", luaB_yieldable},
                                    {NULL, NULL}};

LUAMOD_API int luaopen_coroutine(lua_State* L)
{
    luaL_newlib(L, co_funcs);
    return 1;
}
